Rezultaty
A photographic identification leaflet for the aquaculture industry in Shetland was developed. This guide may be used by the industry when monitoring the water for any harmful species of gelatinous plankton, which have the potential to be problematic to the fish resulting in losses. A quick identification is needed of any gelatinous species, which may harm the farmed fish so effective management methods can be put in place to reduce losses.
GelMOD is a complex, general-purpose computer based model used for aquaculture management and general predictions of occurrences of jellyplankton. The model, which can be applied to general shallow water coastal regions, simulates the transport of jellyplankton larvae due to: tidal, wave, wind and Coriolis induced currents.
The transport model uses the finite different method to advect particles throughout the specified domain. Each particle, representing jellyplankton biomass, is given the characteristics of the jellyplankton larvae at various stages of its development. Thus while particles are being advected by the transport module, life-cycle evolution also takes place in parallel routines. The effects of environment, if relevant, on the jellyplankton evolution are incorporated into the model. Effects to be considered are temperature, salinity and nutrient availability.
This new model has high temporal and spatial resolutions model grid spacing can be as close as 50m and a timestep as low as 30seconds are used. This, along with the incorporation of the life-cycle history, is a major advancement in the development of tools for predicting and managing the marine environment.
A photographic identification leaflet for the aquaculture industry in Shetland was developed. This guide may be used by the industry when monitoring the water for any harmful species of gelatinous plankton, which have the potential to be problematic to the fish resulting in losses. A quick identification is needed of any gelatinous species, which may harm the farmed fish so effective management methods can be put in place to reduce losses.
Periphylla periphylla has the same two categories of nematocysts as other coronates (holotrichous isorhizas and heterotrichous microbasic euryteles), with a total of at least six different types. The capsules are very large in comparison to other scyphozoan medusae like Cyanea capillata, Cyanea lamarckii, Chrysaora hysoscella, Aurelia aurita and Rhizostoma octopus. One of the types (the giant eurytele) can reach a length from up to 100µm.
These euryteles are unique in becoming increasingly large with medusa growth, and in being the largest so far described from Scyphozoa. Lightmicroscopical pictures of the six types are shown in this pictural chart. For the examination tissue of fresh captured medusae were squeezed in glycerol on microscopic slides.
This chart show lightmicroscopical figures of the different nematocysts types of P. periphylla and is directed to students and scientist who are interested in this field of work in order to aid the identification and measurement P. periphylla-nematocysts. It will be disseminated on the website of the University of Hamburg.
A photographic identification information leaflet was developed for the aquaculture industry in Shetland. The identification leaflet will be used by the industry when monitoring for harmful species of phytoplankton, which may have the potential to cause fish kills and/or cause shellfish poisonings.
The cultivation of adult jellyfish in aquaria is very difficult. Most species sampled from the sea do not survive net-capture or transportation to the aquarium. Others die after a few days of culturing. Some famous aquaria (e.g. Monterey Bay and Zooaqurium Berlin) are able to cultivate large scyphozoan medusae. After many years of research, these institutions have designed special aquaria with a particular current strong enough to support the buoyancy of medusae but not so strong as to cause damage to the gelatinous animals.
Nevertheless, there is a way for hobby-researchers, teachers or students to follow the life cycle of jellyfish with comparatively simple methods. In most scyphozoan species, the larval stages do not develop to young medusae directly. Instead they develop to a totally different generation of animals, the polyp-generation. The rearing of young polyps is possible for everybody, as they do not grow more than a few millimetres in size and can be cultivated in glass bowls with approximately 200ml of natural or artificial seawater. With a little luck, the production of young medusae and their development can also be followed. The easiest species to rear is the globally distributed moon jellyfish, Aurelia aurita. The rearing instruction for this species is summarized.
Jellyfish can cause substantial reduction of their prey populations. Since individual jellyfish "filter" out prey from the water at a constant rate (the clearance rate), knowledge about the clearance rate of individual jellyfish can be combined with the density of jellyfish to yield data on mortality rates for various preys. A web-site will be published to describe how this is done. The site will include clearance rates for some predator-prey combinations and instructions on how to calculate mortality rates.
The site will be published to allow free access of the information. To maximize the accessibility, the site will be constructed using low-graphics HTML, which facilitates access for users with low-tech computers and poor Internet connections. Potential users could be central and local authorities or companies involved in monitoring programmes or ecosystem assessments. Also scientists, teachers and students could benefit from the site.
Main benefits of this product will be to clarify the process of how to calculate jellyfish-induced mortality rates, but also that it offers useful, previously unknown, quantitative measures of clearance rates for some common jellyfish-prey combinations.
Scyphozoans have complex marginal sense organs (rhopalia) that are responsible for photoreception, equilibrium reception and sensory responses to other stimuli such as touch, chemicals, pressure and temperature. The gravity sensor inside a rhopalium is the statocyst containing crystalline statoliths. The statocyst crystals have a trigonal shape. The crystal faces are indexed as {3 0 2} (headfaces) and {1 0 0} (sidefaces).
The anorganic material of statoliths is calcium sulphate hemihydrate (bassanite). Elemental analyses performed with EDX-spectroscopy show mainly Ca, S and O. Pictures in the chart show how to measure the size of statocysts, the typical shape of the single crystals and the EDX-analyses. The chart is directed to students and scientists who are interested in this field of work in order to aid the identification and measurement scyphozoan statocysts. It will be disseminated on the website of the University of Hamburg.
A database of jellyfish outbreaks in coastal lagoons with emphasis on factors promoting this problem
The outburst and mass occurrence of jellyfish in coastal lagoons is an expanding problem in temperate latitudes of the world. They started to be reported in the Caribbean Sea (México, Venezuela and Colombia) and later were observed in the Mediterranean (e.g. Spain, Croatia, Morocco, Tunisia) and Australia. The number of species involved is increasing and they seem to be good indicators of the factors supporting these environmental changes.
More examples are expected to be reported in the future, especially in coastal areas with increasing human colonization. Coastal lagoons are fragile semienclosed ecosystems that respond quickly to environmental changes caused by anthropogenic activities and pollution. The databank is filled with all the information available in the literature from the coastal lagoons reported and/or investigated up to date.
The main objective and benefits from this product is to encompass all these data in a single source in order to facilitate comparisons between ecosystems and to find relationships that help scientists and environmental politicians to know and understand the origin and development of these jellyfish outbursts.
A manual was developed for monitoring of distribution and abundance of jellyfish (both hydromedusae and scyphomedusae) in Limfjorden (Denmark). The manual was used by the Limfjord county authorities when monitoring jellyfish in Skive Fjord in 2004 and 2005 using different types of jellyfish nets. The manual (in Danish) may be used in other similar monitoring programs.
The study of abundance and distribution of jellyfishes is difficult because usually had a very aggregated distribution. We have developed a simple and relatively economic system to study the structure and distribution of megaplanckton organisms. For this, a underwater camcorder was placed in a steel structure and towed from a boat to a depth of 1,5 meters. In this structure of pyramidal design the camera was oriented filming the square base. All the structure oriented as well in the direction of advance of the boat. Next to the camera we towed a CTD and temperature and salinity data were stored. The camcorder and the CTD were synchronous with the clock of a GPS that registered and sent to a notebook the position every second. We tried to evaluate the abundance and distribution of three species of medusas (Cotylorhiza tuberculata, Rhizostoma pulmo and Aurelia aurita) in a shallow coastal lagoon (Mar Menor, SE of Spain).
We covered all the area with a route in zigzag. After the sampling, in the laboratory we digitalized the videotapes. Taking a minute of film like a transect we counted the medusae that crossed the frame, the density of jellyfishes was calculated with the sailed distance, and temperature and salinity averages of all the data stored in that route was calculated too. This values was assigned to a position and maps of distribution, abundances and hydrographics dates were made. In the process of to see the films we captured the images when a jellyfish crossed near the steel frame and with analysis of image software we measured it. (we used the freeware Image Tools)
This method allow us to obtain higher number of samples and the amount of this is bigger than the obtained with others methods. With this method we obtain less variances in the results of abundance. On the other hand the number of measured individuals were higher too. Also is possible the study of size distributions in different areas of the lagoon. All software used: 1.- Capture and compression of video with VirtualDub 1.6.10 (freeware) http://www.virtualdub.org/index 2.- Processing CTD data. SeaBird software. (freeware) http://www.seabird.com 3.- GPS Mapping software. OziExplorer. (low cost of purchase) http://www.oziexplorer.com 4.- Image analysis with UTHSCSA ImageTool v 3.0 http://ddsdx.uthscsa.edu/dig/itdesc.html --Results--> During years 2003 and 2004 this method for the study of the populations was used in the Mar Menor (SE of Spain). This method was very useful for the study of Cotylorhiza tuberculata and Rhizostoma pulmo in the years of more abundance.
For Aurelia aurita was a bad method because this specie is almost transparent being difficult of count and measured it. The population dynamics and the distribution were studied. We made relationships between the medusae distribution and the hidrology characteristics of the water. Improvements of the system for the future. The use of this method with more precision and try to study the different levels of aggregation.
Capturing the data each second and positioning each individual medusae perhaps we observe differences in this scale and we could explain why are jellyfish in this scale of aggregation. The use of specific software that applies different treatments of colour to the images perhaps allows us to recount and to measure the individuals of Aurelia aurita too.
A photographic identification leaflet for the aquaculture industry in Shetland was developed. This guide may be used by the industry when monitoring the water for any harmful species of gelatinous plankton, which have the potential to be problematic to the fish resulting in losses. A quick identification is needed of any gelatinous species, which may harm the farmed fish so effective management methods can be put in place to reduce losses.
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